In recent years, a demand for causing robots to do tasks such as assembly performed in a factory or the like is now increasing. Amongst these, in a case where a work object (workpiece) of which position and orientation is not constant at all times is handled by a robot, a unit for measuring a position and orientation of the work object is required, and a visual sensor is generally often used as the unit.
However, in a case where the position/orientation of the work object is three-dimensionally indeterminate, a normal camera is lacking in information, and thus an attempt to incorporate a sensor for acquiring three-dimensional information into the apparatus is performed. Besides, in the field of factory automation (FA), there is a demand for measuring the position/orientation of the work object with higher precision and at higher speed, and thus three-dimensional precision measurement technology has become important. The three-dimensional measurement technology includes a light-section method, a stereo method, a time-of-flight (TOF) method, and so forth.
The light-section method is a technique for obtaining three-dimensional information of an object by performing triangulation with the combination of a camera and a slit light projector. This technique enables users to easily obtain three-dimensional information about textureless objects, and has come to be utilized also for industrial robots. The stereo method is a technique for obtaining three-dimensional information by preparing two or more sets of cameras and using a principle of the triangulation from parallax between images. The TOF method is an abbreviation for time of flight, and is a technique for measuring distances by irradiating a target object with light from a light-emitting diode (LED) light source and receiving its reflected light with a sensor (light-receiving unit) and measuring the time.
Then, when handling a work object with a robot, since data (dimensions and computer-aided design (CAD) data) of the work object is often known, there is a method for performing positional measurement by comparing and matching between information obtained with a visual sensor and data. In order to perform position/orientation measurements with higher precision, a technique for using in combination the above-described three-dimensional measurement technology and three-dimensional model fitting using CAD data and the like is also utilized.
Japanese Patent Application Laid-Open No. 09-212643 discusses a three-dimensional model fitting between a measurement object and a model of the measurement object, using feature portions extracted from a captured image of the measurement object. The three-dimensional model fitting is a technique for acquiring a position and/or orientation of the measurement object by matching a feature portion of the measurement object acquired from the captured image with a feature portion of a three-dimensional model that simulates the measurement object. The three-dimensional model fitting is widely used as a technique for obtaining the position and/or orientation of the measurement object from the captured image. However, a settable range for the position and/or orientation of the three-dimensional model at the time of matching between the feature portions is wide, and thus generally huge amounts of computation time are needed by a computer for performing the three-dimensional model fitting.